* Disproportionation is a definite type of redox reaction in which a specie is simultaneously reduced and oxidized to form two different products
* The UV photolysis of mercury(I) chloride
- $\mathrm{Hg}_2 \mathrm{Cl}_2 \rightarrow \mathrm{Hg}+\mathrm{HgCl}_2$
* It is a disproportionation reaction
* Chlorine can assume oxidation states of $-1,+1,+3,+5$, or +7 within the corresponding anions $\mathrm{Cl}^{-}, \mathrm{ClO}^{-}, \mathrm{ClO}_2^{-}$, $\mathrm{ClO}_3^{-}$, or $\mathrm{ClO}_4^{-}$, known commonly and respectively as chloride, hypochlorite, chlorite, chlorate, and perchlorate